Capping Layer Formation Onto a Dual Damescene Interconnect

ABSTRACT

A process for the formation of a capping layer on a conducting interconnect for a semiconductor device is provided, the process comprising the steps of: (a) providing one or more conductors in a dielectric layer, and (b) depositing a capping layer on an upper surface of at least some of the one or more conductors, characterised in that the process further includes: (c) the step of, prior to depositing the capping layer, reacting the dielectric layer with an organic compound in a liquid phase, the said organic compound having the following general formula: (I) where X is a functional group, R is an organic group or a organosiloxane group, Y1 is either a functional group or an organic group or organosiloxane group, and Y2 is either a functional group or an organic group or organosiloxane group, and where the functional group(s) is/are independently selected from the following: NH2, a secondary amine, a tertiary amine, acetamide, trifluoroacetamide, imidazole, urea, OH, an alkyoxy, acryloxy, acetate, SH, an alkylthiol, sulfonate, methanosulfonate, and cyanide, and salts thereof.

The present invention relates to the deposition of a capping layer on aconducting interconnect in a dielectric layer for a semiconductordevice. More particularly, the present invention relates to thetreatment of the dielectric layer prior to the deposition of the cappinglayer.

Semiconductor manufacturers are continuously striving to produce fasterand more complex integrated circuits. One way to achieve this is toreduce the dimensions of the semiconductor circuits, thereby decreasingthe gate (transistor) delay. However, as the dimensions of the circuitsare reduced, the physical properties of the materials making up thecircuits become increasingly important. In particular, as the size ofthe conducting interconnects contained in the circuit, and moreparticularly their width, decreases, the electrical resistance of theinterconnect is proportionately increased. This causes an increasedinterconnect time delay. Until recently, aluminium had beentraditionally used to manufacture these interconnects. However, in orderto combat the problems associated with the reduction in the circuitdimensions, semiconductor manufacturers have decided that copperprovides better material characteristics than aluminium for use ininterconnects because of its lower bulk resistivity, higher heatconductivity and higher melting point, which results in improved speedand reliability performance. In addition, copper also has lower rate ofgrain boundary diffusion, and therefore higher electromigrationresistance.

Copper interconnects have their own associated problems. Copperinterconnects still have a tendency to be degraded by diffusion andelectromigration. A passivating dielectric layer, typically 30 to 50nanometres thick, is usually applied to the exposed top surface of thecopper interconnect. An example of such a dielectric used in this roleis SiCN. However, copper suffers from poor adhesion to dielectrics, andat the moment it is the dielectric/copper interface which is one of themain limiting factors in the reliability of the final semiconductordevice. In addition, dielectrics such as SiCN have a high dielectricconstant (k value), and therefore their presence adds to the k value ofthe dielectric stack of the final semiconductor device. This is alsoundesirable.

In order to combat these problems, a thin capping layer comprising ametal, typically a metallic alloy, may be deposited on the copperinterconnects instead of a more common dielectric such as SiCN. Thecapping layer is also known as a passivation layer.

It will be appreciated that, although the problems of poor adhesion andelectromigration have been described in the context of copper,interconnects made from other materials which suffer from the sameproblems, may also benefit from such a capping layer for the samereasons.

Techniques used to deposit the capping layer comprising the metal ontothe interconnect, such as electro-less deposition, are generallyselective in nature, in that they deposit the capping layer onto theinterconnect but not onto the dielectric surface. However, theselectivity and effectiveness of these techniques is limited by theexistence of defects on the dielectric surface. These defects can causethe formation of bridges during the deposition of the capping layerbetween two neighbouring interconnects, thereby resulting in unwantedelectronic communication between the interconnects, short circuiting thedevice and ultimately causing device failure. These defects includedefects inherent to the dielectric surface. An example of an inherentdefect is micro-scratches on the surface, which may initiate thedeposition of the capping material on the dielectric surface. Inaddition, small areas of metal or metallic oxide residues on the surfacemay also be considered inherent defects. These areas may originate, forexample, from the patterning and deposition of the conducting materialforming the interconnects onto the surface.

For the case where the capping layer is deposited from an electrolessbath solution, these defects may further include contaminants depositedonto the surface from the reaction solution.

When the surface has undergone polishing, such as Chemical MechanicalPolishing, after the deposition of the interconnect, as is usual whencopper is used for the interconnects, there may be additional causes forthese defects. Firstly, inherent defects on the surface may be formedfrom small areas of metal or metallic oxide residues that have not beenremoved from the surface. The deposition of the capping material may beenhanced on these areas. The defects may also include residual particlesfrom the polishing slurry remaining on the surface.

One approach to reduce the impact of the defects is described in U.S.Pat. No. 5,478,436. This describes a cleaning process after electro-lessdeposition in which residual particles and contaminants on thedielectric surface after the electro-less deposition process are removedby a brushing process.

Previous approaches to the cleaning of the dielectric and interconnectsurfaces prior to deposition of the capping layer have included washingwith both inorganic acids and bases. However, the effectiveness of theseprocesses is limited. Two other approaches are described in U.S. Pat.No. 6,860,944 and US2001/0018266.

U.S. Pat. No. 5,358,743 describes the treatment of a dielectric surfacewith ClSi(CH₃)₃. The treatment is undertaken prior to deposition of acopper interconnect structure in order to increase the selectivity ofthe copper deposition through Chemical Vapour Deposition.

Accordingly, in a first aspect the present invention provides a processfor the formation of a capping layer on a conducting interconnect for asemiconductor device, the process comprising the steps of:

-   (a) providing one or more conductors in a dielectric layer, and-   (b) depositing a capping layer on an upper surface of at least some    of the one or more conductors,    -   characterised in that the process further includes:-   (c) the step of, prior to depositing the capping layer, reacting the    dielectric layer with an organic compound in a liquid phase, the    said organic compound having the following general formula:

where X is a functional group, R is an organic group or a organosiloxanegroup, Y₁ is either a functional group or an organic group ororganosiloxane group, and Y₂ is either a functional group or an organicgroup or organosiloxane group, and where the functional group(s) is/areindependently selected from the following: NH₂, a secondary amine, atertiary amine, acetamide, trifluoroacetamide, imidazole, urea, OH, analkyoxy, acryloxy, acetate, SH, an alkylthiol, sulfonate,methanosulfonate, and cyanide, and salts thereof.

Herein, an organic group describes a group that is bonded to the siliconin Formula I through a carbon atom.

The organic compound may either be provided in neat liquid form or insolution. It will be understood that, although a compound with Formula Imay be provided for reaction with the dielectric surface, hydrolysis atthe silicon atom bearing the functional group(s) may often occur insolution by reaction with water. In this case, it will be appreciatedthat it is not the compound shown by Formula I which undergoes actualreaction with the surface. Instead it may be a compound containing Si—OHbonds, or oligomers of Formula I, in which molecules have reacted tocreate Si—O—Si bonds. The present invention therefore also provides thein situ reaction of compounds having Formula I with water, followed byreaction of the hydrolysis products of Formula I with the dielectricsurface.

Functionalization of the dielectric surface by reacting the dielectricsurface with the organic compound may serve to reduce the number and/orthe effect of the defects on the dielectric surface. Accordingly, thefunctionalization may reduce the reactivity of the dielectric surfaceand defects contained on the surface. The functionalization maysterically shield the surface and the defects. These two effects maycontribute to a further reduction in the rate of deposition of thecapping layer onto the dielectric surface, thereby increasing theselectivity of the deposition process. The functionalization may alsoserve to modify the surface properties of the dielectric surface. Thismay not only be result of the steric shielding and a change ofreactivity, but may also be a result of a change of, for example, thewetting properties of the surface. Accordingly, the functionalizationcan result in a reduced rate of deposition of contaminants onto thedielectric surface. The functionalization of the dielectric surface mayalso serve as an initial cleaning process before the deposition of thecapping layer, displacing impurities already on the dielectric surface.For example, impurities remaining on the surface after the deposition ofthe interconnect material may be removed. These impurities may include,for example, residues, such as silica residues or carbon residues,remaining on the surface if the surface has undergone polishing prior tothe deposition of the capping layer.

Functionalization of the dielectric surface will typically involvedepositing the organic compound on the dielectric surface with theformation of chemical bonds between the compound and the surface. It isalso possible that physical interaction may occur, such as throughhydrogen bonding, electrostatic interactions or even van der Waalsinteractions may be formed, either independently of any chemical bondsor in conjunction therewith.

The functional groups in Formula I may also be described as leavinggroups. Although not wishing to be limited by theory, reaction of theorganosilicon compound with the surface will usually proceed with thenucleophilic substitution of the leaving group by either water, anucleophilic catalyst, or by the hydroxyl groups of the surface itself.Therefore, in this case, a leaving group is preferably defined as agroup that is able to be displaced by a nucleophile under the reactionconditions.

In the present invention the functional group(s) in respect of X andoptionally Y₁ and optionally Y₂ in formula (I) is/are independentlyselected from NH₂, a secondary amine, a tertiary amine, acetamide,trifluoroacetamide, imidazole, urea, OH, an alkyoxy, acryloxy, acetate,SH, an alkylthiol, sulfonate, methanosulfonate, and cyanide, and saltsthereof.

The selection of the functional groups in Formula I, for example NH₂,has been found to lead to a sufficient rate of reaction with thedielectric surface for practical applications. In contrast, some otherfunctional groups, such as halogens (eg chlorine), may exhibit arelatively slow rate of reaction with the surface. A slow rate ofreaction is undesirable for practical applications since it increasesthe processing time and reduces the efficiency of the overall productionprocess. Furthermore, a halogen functional group, for example chlorine,may result in the formation of undesirable by-products, which maynecessitate further processing steps.

The consideration of the rate of reaction is especially important whencertain preferred methods of applying the solution to the surface areconsidered. For example, a fast reaction time is especially required inan application where the organosilicon compound is sprayed, either inneat form or in solution, onto the surface of the dielectric. This isthe case because it is expected that the reaction solvent may quicklyevaporate from the dielectric surface.

Gas phase functionalization of a surface by an organosilicon compoundinvolves intricate apparatus and the need for very carefully controlledreaction conditions. However, the present inventors have found that, forthis pre-treatment step prior to the deposition of a capping layer on aconducting interconnect, liquid phase processing may be a much morepractical technique for processing a substrate. This is because it maybe carried out in the same apparatus as the deposition of the cappinglayer, and therefore removes the need for specialized apparatus for thefunctionalization of the surface.

Advantageously, the functional group X and optionally Y₁ and/or Y₂ areindependently selected from a primary amine, secondary amine, andtertiary amine, including salts thereof.

In a preferred embodiment, Y₁ is a functional group, and the functionalgroup comprises an amino group or protonated derivative thereof. In apreferred embodiment, the organic compound comprises a reactiveorganofunctional siloxane oligomer, which may be provided in water.

In another preferred embodiment, Y₁ and Y₂ are independently selectedorganic groups and/or organosiloxane groups, so that a total of threeindependently selected organic groups and/or organosiloxane groups areattached to the silicon. This may be advantageous since it may provideenhanced shielding of the surface.

Preferably, the silicon in the organosilicon compound bears twoindependently selected functional groups and two independently selectedorganic groups and/or organosiloxane groups. In another embodiment, thesilicon bears one functional group and three independently selectedorganic groups and/or organosiloxane groups. These embodiments areconsidered advantageous, as having two or more organic and/ororganosiloxane groups attached to the silicon may be able to bettershield the defects on the surface. In other words, the steric bulk ofthe organic and/or organosiloxane groups may be advantageous, andtherefore the incorporation of more organic and/or organosiloxane groupsonto the silicon may enhance the steric shielding of the surface. Thismay help protect and reduce the reactivity of any nucleation sites onthe surface. Furthermore, by incorporating two or more organic and/ororganosiloxane groups onto the silicon, the surface may be more able torepel water than with only one organic group. Hydration of the surfaceand bulk is kept to a minimum, and therefore, as described below, thedielectric constant of the dielectric layer is also kept to a minimum.

In addition, at least one of the organic groups preferably contains abranching point, such as in a tert-butyl group. These groups are thoughtto provide an ‘umbrella’ for the dielectric surface, thereby providingenhanced protection of the defects on the surface. Additional protectionof the dielectric surface may be provided by groups containing two ormore branching points, such as by a 2,2,3-trimethylbutyl group.

Preferably, the organosiloxane is an organosiloxane oligomer ororganosiloxane polymer. More preferably, it has the general formula:

where Y₁, Y₂, Y₃, Y₄ and Y₅ are independently selected functional groupsas defined in claim 1 and/or organic groups, and n is a positiveinteger.

Preferably, n is in the range of 1 to 20. More preferably, n is in therange of 1 to 5.

Examples of organosilicon compounds include: hexamethyl-disilazane,trimethyldimethylaminosilane, dimethyl-t-butyldimethylaminosilane, andbi-functional dimethylbis(dimethylamino)silane. Examples of watersoluble organosilanes include Dynasylan HS2627 and HS2909, supplied fromDegussa. These are organo amino-silanes further comprising organogroups. A further example is Silicad from Gelest, Inc., which has thechemical formula C₁₈H₃₇Si(OH)₃.

Nucleophilic catalysts may also be added to the reaction solution.Examples of additives include methanol, ethanol, ammonia and pyridine.These may also be added to enhance the solubility of the organosiliconcompound.

Advantageously, R and optionally one or both of Y₁ and Y₂ is/areindependently selected from the following organic groups ororganosiloxanes: a organosiloxane oligomer, a organosiloxane polymer,C1-C25 alkyl, C2 to C25 alkenyl, C2 to C25 alkynyl, aryl, arylsubstituted with one or more of C1-C25 alkyl, C2-C25 alkenyl and/orC2-C25 alkynyl. Any of these may be partially or fully halogenated.Preferably, R and optionally one or both of Y₁ and Y₂ is/areindependently selected from methyl, ethyl, propyl, butyl, phenyl,pentafluorophenyl, 1,1,2-trimethylpropyl (thexyl) and allyl. Again, anyof these may be partially or fully halogenated.

The dielectric surface preferably contains hydroxyl groups or groupsthat hydrolyze in an ambient aqueous environment to produce hydroxylgroups. In this case, the functionalization of the dielectric surfacepreferably involves interaction, preferably reaction, of the surfacegroups.

Accordingly, the present invention is able to provide a furtheradvantage. It is often the case that the dielectric constant of thesurface is greater than that of the bulk. One reason for this may be thepresence of hydroxyl groups on the surface of the dielectric. Thesehydroxyl groups may result in the favourable absorption of water ontothe surface. The absorbed water is believed to lead to an increaseddielectric constant at the surface. In addition, if the dielectriccomprises a porous material, then the water molecules may absorb intothe bulk material through the penetration of pores, causing an increasein the bulk dielectric constant. Therefore, by functionalizing thesurface through interaction or reaction of the hydroxyl groups, theabsorption of water onto the surface may become less favoured, therebyreducing the surface dielectric constant. If the dielectric layer isporous, then the functionalization may also keep to a minimum theincrease in the bulk dielectric constant due to the absorption of water.

In the case of a silicon-oxide-containing material, surface hydroxylgroups are generated by the break up or hydrolysis of Si—O—Si (siloxane)bonds at the surface of the material by reaction with moisture. Thesebonds are usually strained since they are typically part of four- orsix-membered siloxane rings. In addition, in other materials, such asmetal oxides, hydroxyl groups may also be formed at the surface byreaction with moisture.

Hydration of the surface, and hydration of the bulk material in the caseof a porous dielectric, is a particularly relevant issue. An advantageof the present invention is that it is able to address certain problemsassociated with hydration. Firstly, when the surface undergoes polishingprior to the formation of the capping layer, this is usually carried outin the presence of a water-based slurry. Therefore the treatment of thesurface with an organic compound which interacts or reacts with thesurface hydroxyl groups may also serve to dehydrate the surface at thesame time (by reaction with absorbed water), and it may also lead to thedehydration of the bulk material. In this way, the dielectric constantof the dielectric material may advantageously be reduced.

Secondly, if the capping layer is deposited onto the conductinginterconnect from an aqueous solution, the presence of an organic layeron the dielectric surface may reduce the rate of, or prevent, waterabsorption onto the dielectric surface during the deposition process.This again may keep the dielectric constant of the dielectric surfaceand the dielectric bulk to a minimum.

This may have the additional advantage of widening the range of methodsthat can be used to process a semiconductor device, in particular asemiconductor device containing a porous dielectric. Therefore ChemicalMechanical Polishing and electro-less deposition may be used now withoutthe need to take any steps to minimize hydration of the surface duringthese processes.

Preferably, the process for the formation of the capping layer furthercomprises, prior to the step of functionalizing the upper surface of thedielectric layer, the step of polishing the upper surface of theconductors so that said surface is substantially co-planar with theupper surface of the dielectric. The step of polishing the upper surfaceof the one or more conductor(s) preferably comprises the conventionaltechnique of chemical mechanical polishing (CMP). In this case, thepre-treatment of the dielectric surface prior to deposition of thecapping layer has the further advantage that it may lead to thedisplacement of residuals remaining on the surface after polishing.

The one or more conductors preferably comprise Cu or an alloy thereof.Alternatively, or in conjunction, Ag or an alloy thereof may be used.

The dielectric layer preferably comprises an oxide of silicon or acarbonated oxide of silicon. Suitable examples include silicon dioxideor carbonated silicon dioxide. The dielectric layer may be a porous ornon-porous layer.

The capping layer will typically comprise a metal, typically a metalalloy, preferably a ternary alloy, composition comprising, for example,one or more of Co, Ni, W, Mo, B, P and Sn. Suitable examples includeCoP, CoB, CoWP, CoWB, CoMoB, CoWBP, NiP, NiB, NiMoP, and CoSnP.

The capping layer is preferably deposited by a process comprisingelectro-less deposition. The process is selective, so that the cappinglayer is essentially only deposited on the interconnect structure andnot on the dielectric surface. The process involves placing the surfacecontaining the interconnects into a solution of the salts of the variousmetals to be incorporated into the alloy capping layer. A reducing agentis usually incorporated into the solution. It is thought that thereducing agent may facilitate the reduction of the metal salts to themetal. An acid or base which alters the pH of the solution may also beadded to the solution. In addition, a salt may be added to buffer thesolution. Surfactants and/or complexing agents can also be incorporatedinto the plating solution.

A solution for the electroless deposition of CoWP may, for example,comprise a tungstate salt (WO₄ ²⁻), such as a sodium salt, an ammoniumsalt or the tetramethylammonium salt; a cobalt salt, such as a chlorideor sulphate; a hypophosphite, such as a sodium salt, an ammonium salt orthe tetramethylammonium salt; EDTA may be added as a complexing agent;and tetra-methyl-ammonium-hydroxide may be added to alter the pH.Citrate ions may be added to buffer the solution. Each of thesecomponents are added to the solution in a proportion in the range of 5to 100 g per litre of water solvent. In addition, a surfactant may beadded at a lower concentration, such as in the range of 0.1 to 5 g perlitre of solution. Preferably, the reaction solution is kept in thetemperature range 40 to 90° C., more preferably between 45 and 60° C.The pH of the solution may be between 8.5 and 13, preferably between 8.5and 9.5. Further details of techniques for electroless deposition formetallic cap layers can be found in Electrochim. Acta 44, 3639-3649(1999).

When reaction of the dielectric surface with the organosilane is carriedout in solution, care may need to be taken in order to avoid excessivepolymerization of the reactant. Excessive polymerization ischaracterized by the reaction solution turning cloudy. Polymerizationis, for example, favoured by a high concentration of reactant.Therefore, the concentration of the compound having Formula I, or itshydrolysis product, is preferably in the range of 10⁻⁴ to 10⁻² moldm⁻³.

Other favoured reaction conditions include a reaction temperature offrom 20 and 85° C., preferably 20 to 50° C. The length of time that thedielectric layer is left exposed to the reaction solution is preferablyup to 240 minutes; more preferably up to 30 minutes; more preferablybetween 20 seconds and 5 minutes; and more preferably up to 2 minutes.

The compounds having Formula I may also be applied to the surface byspraying. More particularly, the compounds may be dissolved in anorganic solvent and sprayed onto the surface, or the compounds may beapplied to the surface in neat form. Preferably, the compounds may besprayed onto the surface in an inert atmosphere. The inert atmosphereshould principally contain very little or no moisture (e.g. preferably<1% humidity). In addition, the inert atmosphere may contain one or morethe following gasses: argon, nitrogen, and/or carbon dioxide.

Functionalization may also be achieved by the Langmuir-Blodgetttechnique.

The organosilicon compound may be added either in a solution by itself,or in a solution containing additives. In either case, the treatment ofthe surface with the solution containing the organic component mayprecede, or be preceded by, or both be preceded by and precede, thecleaning of the surface. This cleaning (or washing) may include eitherone or two steps:

-   -   a) treatment with an inorganic acid or inorganic base, such as        ammonium persulfate, ammonium phosphate, ammonium fluoride or        ammonium hydroxide;    -   b) treatment with an organic acid or an organic base, such as        citric acid, oxalic acid, malic acid, acetic acid, tartaric        acid, tetramethylammonium hydroxide, tetraethylammonium        hydroxide, aminoethanol.

These steps may be carried out either in order (i.e. step a followed bystep b), or in reverse (i.e. step b followed by step a), or one can becarried out before treatment step of the present invention with theorganic component, and the other after, or with one or both stepsbefore, or with one or both steps after.

In a preferred embodiment, steps a and b are carried out prior to thetreatment of the surface with a solution containing only an organiccomponent, more preferably an organosilicon compound, such as that withthe structure of Formula I, to functionalize the dielectric surface.

The pre-treatment solution may comprise one of or more of water and anorganic solvent. Preferably, especially when the pre-treatment solutionis water-based, a co-solvent is included. The co-solvent may enhance thesolubility of the components of the solution, such as the surfactant. Inaddition, the co-solvent may allow the reaction solution, and thedistribution of the components in the solution, to be more homogenouscompared to without the presence of the co-solvent. Preferably, theco-solvent is an alcohol, more preferably it is ethanol and/or isopropylalcohol (IPA).

In addition to the component having Formula I, the pre-treatmentsolution may also include a number of other additives.

For example, the solution may include complexing agents, such as EDTA(ethylenediaminetetraacetic acid), or a derivative or salt thereof.Complexing agents are able to help the removal of any metallic speciesabsorbed onto the surface. The organic acid may also act as a complexingagent.

The pre-treatment solution may also include surfactants to aid thewetting of the pre-treatment solution onto the surface, to aid thesolubility of various of the components in solution, and/or to helpclean the surface. A wide variety of surfactants may be used. It may beadvantageous to use a block co-polymer of poly(ethyleneoxide) andpoly(propylene)oxide. These two groups are efficiently absorbing on bothhydrophobic and hydrophilic surfaces, and the length and ratio of eachgroup present in the block co-polymer can be easily tailored to theapplication.

The pre-treatment solution may be either acidic or basic. In the casewhere neither steps a or b described above are carried out before orafter treatment of the surface with this pre-treatment solution, thepre-treatment solution preferably has a pH of less than 3. Accordingly,the pre-treatment solution may include an acid, preferably an organicacid, for example citric and/or malic acid. The pre-treatment solutionmay also include an inorganic acid, for example an ammonium salt, suchas ammonium persulfate.

It will be apparent from the foregoing that the present inventionprovides a pre-clean step for selective electroless deposition insemiconductor fabrication.

In a second aspect, the present invention provides a process for theformation of a capping layer on a conducting interconnect for asemiconductor device, the process comprising the steps of:

-   -   providing one or more conductors in a dielectric layer, the one        or more conductors comprising Cu or an alloy thereof, the        dielectric layer comprising Si or an oxide or carbonated oxide        thereof, and    -   depositing a capping layer on an upper surface of the one or        more conductors,    -   characterised in that, prior to depositing the capping layer,        the process further includes the step of reacting an upper        surface of the dielectric layer with a reactive organofunctional        organosiloxane oligomer.

The reactive organofunctional siloxane oligomer may be provided in thepresence of water

The features described above in relation to the first aspect are alsoapplicable to the second aspect, either singularly or in combination.

In a third aspect, the present invention provides a conductinginterconnect for a semiconductor device obtainable by a process asherein described.

In a fourth aspect, the present invention provides a conductinginterconnect for a semiconductor device, comprising:

(i) a dielectric layer having one or more conductors provided in anupper surface thereof, said upper surface being functionalized so as toreduce the number and/or the effect of any defects on the dielectricsurface or to modify the surface properties of the dielectric surface,and(ii) a capping layer provided on an upper surface of at least some ofthe one or more conductors.

In a fifth aspect, the present invention provides a semiconductor devicecomprising a conducting interconnect as herein described.

In a sixth aspect, the present invention provides for the use of anorganic compound to functionalise a dielectric layer having one or moreconductors on a surface thereof, wherein said use comprises reacting theorganic compound with the dielectric layer prior to deposition of acapping layer on an upper surface of at least some of the one or moreconductors, and wherein said organic compound has the following generalformula:

where X is a functional group, R is an organic group or a organosiloxanegroup, Y₁ is either a functional group or an organic group ororganosiloxane group, and Y₂ is either a functional group or an organicgroup or organosiloxane group, and where the functional group(s) is/areindependently selected from the following: NH₂, a secondary amine, atertiary amine, acetamide, trifluoroacetamide, imidazole, urea, OH, analkyoxy, acryloxy, acetate, SH, an alkylthiol, sulfonate,methanosulfonate, and cyanide, and salts thereof.

The features described above in relation to the first aspect are equallyapplicable to the second, third, fourth, fifth and sixth aspects, eithersingularly or in combination.

EXAMPLES

The present invention will now be illustrated further with reference tothe following non-limiting examples

Comparative Example 1

A conventional array of copper interconnects on a silicon dioxidesurface was provided after Chemical Mechanical Polishing. A solutioncontaining 20 g citric acid, 20 g malic acid and 20 g ammoniumpersulfate in 1 litre of water was prepared. The pH of the solution wasmeasured to be between 2.8 and 2.9. The silicon dioxide/copperinterconnect surface was immersed in this solution at 22° C. for 2minutes in a beaker. The surface was then transferred into a solutionfor the electroless deposition of a capping layer, as described inpatent application number US2005/0048773 (U.S. Pat. No. 6,924,232) inthe name of Freescale. The solution was treated for 50 seconds at 55°C., and then removed from the solution, and allowed to dry.

A photograph of the surface is shown in FIG. 1. Portions on thedielectric surface onto which the capping layer has been deposited areclearly visible as spots of darker material on the lighter dielectricsurface. It is thought that this unselective deposition of the cappinglayer is a result of residuals on the dielectric surface.

Example 1

A conventional array of copper interconnects on a silicon dioxidesurface was provided after Chemical Mechanical Polishing. A solutioncontaining 20 g citric acid, 20 g malic acid and 20 g ammoniumpersulfate in 1 litre of water was prepared. To this was added 0.5 wt %Sivento Dynasylan HS2627. Sivento Dynasylan HS2627 was supplied byDegussa, and it is known to be a siloxane oligomer that is soluble inwater. This siloxane oligomer further comprises an amino functionalgroup and organic groups attached to silicon. The pH of the solution wasmeasured to be 2.9. The silicon dioxide/copper interconnect surface wasimmersed in this solution at 22° C. for 2 minutes in a beaker. Thesurface was then transferred into a solution for the electrolessdeposition of a capping layer, as described in patent application numberUS20050048773 in the name of Freescale. The solution was treated for 50seconds at 55° C., and then removed from the solution, and allowed todry.

A photograph of the surface is shown in FIG. 2. Unlike for thecomparative example 1, a clean surface is observed, indicating a muchmore selective deposition of the capping layer than in the case of thecomparative example.

1. A process for the formation of a capping layer on a conductinginterconnect for a semiconductor device, the process comprising thesteps of: (a) providing one or more conductors in a dielectric layer,and (b) depositing a capping layer on an upper surface of at least someof the one or more conductors, characterised in that the process furtherincludes: c) the step of, prior to depositing the capping layer,reacting the dielectric layer with an organic compound in a liquidphase, the said organic compound having the following general formula:

wherein X is a functional group, R is an organic group or aorganosiloxane group, Yi is a functional group or an organic group ororganosiloxane group, and Y₂ is a functional group or an organic groupor organosiloxane group and wherein the functional group (s) is/areindependently selected from the following NH₂, a secondary amine, atertiary amine, acetamide, trifluoroacetamide, imidazole, urea, OH, analkyoxy, acryloxy, acetate, SH, an alkylthiol, sulfonate,methanosulfonate, and cyanide, and salts thereof, and wherein at leastone of the organic groups contains one or more branching points.
 2. Aprocess as claimed in claim 1, wherein, prior to the step of reactingthe dielectric layer with the organic compound, the process furtherscomprises the step of polishing the upper surface of the one or moreconductors so that said surface is substantially co-planar with theupper surface of the dielectric.
 3. A process as claimed in claim 2,wherein the step of polishing the upper surface of the one or moreconductors comprises chemical mechanical polishing (CMP).
 4. A processas claimed in claim 1, wherein the one or more conductors comprises Cuor an alloy thereof or Ag or an alloy thereof.
 5. A process as claimedin claim 1, wherein the dielectric layer comprises an oxide of siliconor a carbonated oxide of silicon.
 6. A process as claimed in claim 5,wherein the dielectric layer comprises silicon dioxide or carbonatedsilicon dioxide.
 7. A process as claimed in claim 1, wherein thedielectric layer is a porous layer.
 8. A process as claimed in claim 1,wherein the capping layer comprises an alloy.
 9. A process as claimed inclaim 8, wherein the capping layer comprises a ternary alloycomposition.
 10. A process as claimed in claim 9, wherein theternary-alloy composition comprises one or more of Co, Ni, W, Mo, B, Pand Sn.
 11. A process as claimed in claim 1, wherein the capping layercomprises CoP, CoB, CoWP, CoWB, CoMoB, CoWBP, NiP, NiB, NiMoP or CoSnP.12. A process as claimed in claim 1, wherein the capping layer isdeposited by electroless deposition.
 13. A process as claimed in claim1, wherein R and optionally one or both of Y₁ and Y₂ is/areindependently selected from the following organic and organosiloxanegroups: a organosiloxane oligomer, or organosiloxane polymer, C1-C25alkyl, C2 to C25 alkenyl, C2 to C25 alkynyl, aryl, aryl substituted withone or more of C1-C25 alkyl, C2-C25 alkenyl and/or C2-C25 alkynyl.
 14. Aprocess as claimed in claim 13, where the organosiloxane oligomer ororganosiloxane polymer has the general formula:

wherein n is a positive integer, and wherein Y₁ is a functional group oran organic group, Y₂ is a functional group or an organic group, Y₃ is afunctional group or an organic group, Y₄ is a functional group or anorganic group, and Y₅ is a functional group or an organic group, andwherein the functional group (s) is/are independently selected from NH₂,a secondary amine, a tertiary amine, acetamide, trifluoroacetamide,imidazole, urea, OH, an alkyoxy, acryloxy, acetate, SH, an alkylthiol,sulfonate, methanosulfonate, and cyanide, and salts thereof.
 15. Aprocess as claimed in claim 14, wherein n is in the range of 1 to 20.16. A process as claimed in claim 15, wherein n is in the range of 1 to5.
 17. A process as claimed in claim 1, wherein at least one of theorganic groups contains at least two branching points.
 18. A process asclaimed in claim 1, wherein the compound having Formula I is hydrolyzedprior to reaction with dielectric surface.
 19. A process as claimed inclaim 1, wherein the step of reacting the dielectric surface with theorganic compound is carried out in a solvent comprising an organicsolvent.
 20. A process claimed in claim 1, wherein the step of reactingthe dielectric surface with the organic compound is carried out in asolvent comprising water.
 21. A process as claimed in claim 1, whereinthe step or reacting the dielectric surface with the organic compound iscarried out in a solution comprising an acid and/or a surfactant.
 22. Aprocess for the formation of a capping layer on a conductinginterconnect for a semiconductor device, the process comprising thesteps of: providing one or more conductors in a dielectric layer, theone or more conductors comprising Cu or an alloy thereof, the dielectriclayer comprising Si or an oxide or carbonated oxide thereof, anddepositing a capping layer on an upper surface of the one or moreconductors, characterized in that, prior to depositing the cappinglayer, the process further includes the step of reacting an uppersurface of the dielectric layer with a reactive organofunctionalorganosiloxane oligomer.
 23. A process as claimed in claim 22, whereinthe reactive organofunctional organosiloxane oligomer is provided in thepresence of water.
 24. A conducting interconnect for a semiconductordevice obtainable by a process as defined in claim
 1. 25. A conductinginterconnect for a semiconductor device, comprising: (i) a dielectriclayer having one or more conductors provided in an upper surfacethereof, said upper surface being functionalized by reacting thedielectric surface with an organic compound in a liquid phase, the saidorganic compound having the following general formula:

wherein X is a functional group, R is an organic group or aorganosiloxane group Yi is either a functional group or an organic groupor organosiloxane group, and Y₂ is either a functional group or anorganic group or organosiloxane group, and wherein the functional group(s) is/are independently selected from NH₂, a secondary amine, atertiary amine, acetamide, trifluoroacetamide, imidazole, urea, OH, analkyoxy, acryloxy, acetate, SH, an alkylthiol, sulfonate,methanosulfonate, and cyanide, and salts thereof, and wherein at leastone of the organic groups contains one or more branching points; and(ii) a capping layer provided on an upper surface of at least some ofthe one or more conductors.
 26. A conducting interconnect as claimed inclaim 25, wherein the organic compound is a reactive organofunctionalsiloxane oligomer.
 27. A conducting interconnect as claimed in claim 25,wherein the one or more conductors comprises Cu or an alloy thereof orAg or an alloy thereof.
 28. A conducting interconnect as claimed inclaim 25, wherein the dielectric layer comprises an oxide of silicon ora carbonated oxide of silicon.
 29. A conducting interconnect as claimedin claim 28, wherein the dielectric layer comprises silicon dioxide orcarbonated silicon dioxide.
 30. A conducting interconnect as claimed inclaim 25, wherein the dielectric layer is a porous layer.
 31. Aconducting interconnect as claimed in claim 25, wherein the cappinglayer comprises an alloy.
 32. A conducting interconnect as claimed inclaim 31, wherein the capping layer comprises a ternary alloycomposition.
 33. A conducting interconnect as claimed in claim 32,wherein the ternary alloy composition comprises one or more of Co, Ni,Mo, B, P and Sn.
 34. A conducting interconnect as claimed in claim 25,wherein the capping layer comprises CoP, CoB, CoWP, CoWB, CoMoB, CoWBP,NiP, NiB, NiMoP or CoSnP.
 35. A conducting interconnect as claimed inclaim 25, wherein the capping layer is an electroless deposited cappinglayer.
 36. A semiconductor device comprising a conducting interconnectas defined in claim
 25. 37. Use of an organic compound to functionalizea dielectric layer having one or more conductors on a surface thereof,wherein said use comprises reacting the organic compound with thedielectric layer prior to deposition of a capping layer on an uppersurface of at least some of the one or more conductors, and wherein saidorganic compound has the following general formula:

wherein X is a functional group, R is an organic group or, aorganosiloxane group, Yi is either a functional group or an organicgroup or organosiloxane group, and Y₂ is either a functional group or anorganic group or organosiloxane group, and wherein the functional group(s) is/are independently selected from NH₂, a secondary amine, atertiary amine, acetamide, trifluoroacetamide, imidazole, urea, OH, analkyoxy, acryloxy, acetate, SH, an alkylthiol, sulfonate,methanosulfonate, and cyanide, and salts thereof, and wherein at leastone of the organic groups contains one or more branching points.